Generating apparatus



Dec.- 8, 1942. B. CASSEN GENERATING APPARATUS Filed Ma 2, 1940 I INVENTOR 56776070! 0055672.

ATT

WITNESSE S: m

Patented Dec. 8, 1942 UNITED STATES PATENT OFFICE GENERATING APPARATUS Benedict Cassen, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 2, 1040, Serial No. 332,932

11 Claims.

My invention relates to apparatus for generating high frequency electrical oscillations and has particular relation to the generation and transmission of oscillations having a wavelength of the order of several decimeters.

It is an object of my invention to provide apparatus for efliciently transmitting high frequency oscillations.

Another object of my invention is to provide' electrical oscillations of high frequency.

My invention arises from the realization that several dielectric materials may be arranged in layers in such manner that they transmit oscillations impinging thereon with inconsequential losses at the boundary surfaces. High frequency radiant energy may thus be transferred without substantial loss to a low loss dielectric channel for transmission by interposing one or more layers of other dielectric material having properly selected properties. Preferably a single layer of a low dielectric constant material having a thickness substantially equal to one-quarter of the wavelength of the oscillations in the material is interposed. In general, the thickness may be equal to any odd number of quarters of the wavelength. Because of the interference which exists at the boundary between the outside atmosphere and the low dielectric constant material, the reflected wave is substantially suppressed and the total energy impinging on the layer is transmitted through the high dielectric constant channel.

The most propitious relationship between the dielectric constants of the materials may be derived mathematically. Let k be the dielectric constant of the material on which the high frequency waves first impinge and K the dielectric constant of the low loss channel. In sucha case the reflection coemcient as applied to the amplitude of a wave transmitted through air and impingingpn the material of dielectric constant k is equal to II? -1 ml The reflection coeflicient for a wave passing lromthe medium of constant k to that of constant K is equal to I v1 +v k The coefiicient which measures the transmission of the wave impinging on the material kirom air is equal to 1 less the coeflicient measuring the reflection, and therefore the former is equal 1 1 H0 +1 This coeflicient represents the energy which is incident on the boundary between the two dielectric materials. The portion reflected from the boundary is in such a case represented by the incident energy multiplied by the coefiicient-of reflection for the boundary or (I w-1 42- vk+1 i/ +-/k As the wave reflected from the inner dielectric layer is transmitted through the boundary between the dielectric k and air, it is again reflected at the latter boundary and the portion transmitted is measured by the coeflicient or any other odd number of quarter wavelengths A where n is an even integer, where A is the wavelength of the oscillations in air or 8.. vacuum. In such a case the wave impinging on the dielectric lc from the air and .refiected may be counteracted by the wave returning from the inter-dielectric .layer if their amplitudes are equal. The condition for equal amplitudes is that the coeflicient last derived shall be equal to the coefficient of reflection of the original wave. That is to say I 412-1 wit-412415 "4H via/E v11 irom'which it appears that The thickness of the incident layer is in such a case The dielectric constant of the channel is K k +5 k 81 Materials having a dielectric constant 81 are not so frequently encountered as those havin a constant of the order of 9. However, I have found that rutile,.a crystal form of titanium dioxide, has a constant'of the order of 100 and it may be utilized with advantage in the present situation. Other materials such as water. have also been found to be useful. When titanium oxide is used in the practice of my invention, it may be provided in the form of a powder and packed as tightly as the situation may require. The powdered rutile may also be properly treated and fired to form a compact solid.

In the actual practiceof my invention, I provide an arrangement for transmitting high frequency oscillations which comprises an incident layer of a low dielectric constant substance such as polysterene, a phenolic condensation product, compressed paper, artificial resin or other similar materials to which a channel comprising a container filled with finely divided or fired rutile is contiguous. The channel may be bent in any desired form to direct the radiant energy as may be required. At the receiving end a further layer of the low dielectric constant material may be provided to suppress reflection losses. In both cases the thickness of the matewhich is to function as an electrical resonator is filled with rutile or any other high dielectric constant material. Because of the effect of the dielectric. the hollow body may be smaller for a given wavelength and the attenuation is substantially decreased The radiation of energy from the resonator is expedited by the interposition of a quarter wavelength layer of a suitable low dielectric constant material.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof will best be understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic view showing an embodiment of my invention, and

- Fig. 2 is a diagrammatic view showing a modification of my invention.

The apparatus shown in Fig. 1 comprises a hollow container 3, preferably composed of sheet metal which is highly evacuated. At one end of the container an emissive filament 5 is disposed. The filament may be heated in the usual manner from a source 1 available, symbolically shown as a battery. The filament 5 is enclosed within a metallic cap 9 having a small perforation H in its center. The cap 9 is connected directly to ground and the filament is connected to the negative terminal of a power source it, preferably of the order of several thousand volts.

Because of the field between the filament I and the cap 9, electrons are drawn from the filament and concentrated into a narrow beam as they pass through the perforation H. The electron beam then passes through a pair of hollow body resonators l5 and i1 disposed within the container 3. Each resonator is a hollow doughnut shaped conductor, preferably composed of sheet metal and disposed with its axis of revolution along the line of the electron stream. In the regions of their surfaces which are in the path of the electron stream, the solid sheet metal is replaced by open work l9 so that the stream may pass through the resonators unimpeded. On being emitted from the second resonator II, the electron stream is disposed by a metal plate 2| to the walls of the container which rial is preferably equal to one quarter of the wavelength of the radiation to be transmitted in the material.

In accordance with another aspect of my invention, the principles developed here are used to improve the operation, and the structure of a hollow body resonator. A hollow conductor are, in turn, grounded.

The'resonators I5 and II are so dimensioned that for the mode of electromagnetic oscillation for which the electric field is parallel to the stream, the frequency of one is equal to that for the other. They are coupled together by a conductor 23 so that there is an interchange of the energy between them. Within the resonators, the coupling conductor 23 has the form of a loop so oriented as to be threaded by the magnetic field produced by the oscillations.

As the stream passes through the first resonator IS, a sinusoidal component corresponding to the electrical oscillations existing within the resonator is impressed on the velocity of the electrons. The modulation in the velocity causes the electrons to collect in clusters periodically and the second resonator I1 is so disposed as to absorb energy from the electrons as they pass through it. A portion of the energy absorbed by the second resonator I1 is fed back to the first resonator l5 through the conductor 23 so that a short time after the operation is initiated subantenna 25 :tantial oscillations are built up. Radiant energy may be derived from the second resonator l'l :hrough a suitable antenna 26 coupled thereto.

To transmit the derived energy in any desired direction, a hollow semi-sphere 21 of a material of low dielectric constant is disposed over the so as to receive its radiation. The 21 is embedded ina mass of rutile within a metallic tube 3| bent in a manner corresponding to the direction of transmission desired. The thickness of the wall of the semi-sphere is equal to one quarter of the semi-sphere 29 disposed wave length of the frequency of the radiant energy in the material of which the semi-sphere is composed, i. e., to

where it is the dielectric constant of the ma.- terial and A the wavelength in air or a vacuum. At the emitting end of the channel 29-3l, another layer 33 of the same thickness of the low dielectric constant material may be disposed adjacent to the rutile mass. The dielectric constant of the semi-sphere 21 is so selected with reference to the constant of the rutilethat the reflection at the boundary surfaces is suppressed. The radiant energy generated in the container 3 may thus be guided in any desired manner and emitted at any given point.

In Fig. 2, an eflicient generator of oscillations in accordance with my invention is provided. The structure shown in this view is to a large extent similar to that shown in Fig. 1. However, the resonators 35 and 31 are in this casefilled with rutile 39 so that they may be substantially smaller, while at the same time, they operate with substantially greater efliciency. Moreover, the derivation of radiation from the energy absorbing resonator 31 is carried out in a somewhat more convenient manner than in the Fig. l modification. In this case, a rutile 43 extends from the radiating resonator and the energy is transmitted through the tube ii and through a greater wavelength layer 45 if low dielectric constant material disposed in its end, which is properly selected to suppress :eflection losses. As shown, the energy from the resonator is emitted in the air. However, the :ube ll may have any length and any form desired and may thus be used in the same manner is the rutile channel in Fig. 1.

The resonators disclosed in Figs. 1 and 2 may be provided with the usual additional electrodes and grids as taught in the cathode-ray art. Since .he specific structure of the latter elements does iot primarily concern the present invention, it 12.5 not been disclosed in detail.

Although I have shown and described certain ;pecific embodiments of my invention, I am fully were that many modifications thereof are :ossible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended :laims.

I claim as my invention:

1. In combination, a generator of high frequency electrical oscillations having an output element, a layer of dielectric material having a dielectric constant of the order of cooperative with said element to receive said oscillations and a channel of a dielectric'material having a dielectric constant of the order of 100 contiguous o said layer said layer being dimensioned so that 75 tube 4| filled with said oscillations are passed efflclently from'said layer to said channel.

2. In combination, a generator of high frequency electrical oscillations having an output element, a layer of dielectric material having a diflerent dielectric constant than said element and cooperative with said element to receive said oscillations and a channel of a dielectric material having a dielectric constant of the order of ten times the dielectric constant of said layer contiguous to said layer, said layer being dimensioned so that said oscillations are passed efliciently from said layer to said channel.

3. In combination, a generator of high frequency electrical oscillations having an output element, a layer of dielectric material having a thickness substantially equal to where n is an even integer and i. is the wavelength or said oscillations in said material, cooperative with said element to receive said oscillations and a channel of a dielectric material having a dielectric constant of the order of ten times the dielectric constant of said layer contiguous to said layer so that said oscillations pass from said layer to said channel.

4. In combination, a generator of high frequency electrical oscillations having an output element, a layer of dielectric material having a low dielectric constant and a thickness substantially equal to where n is an even integer and A is the wavelength of said oscillations cooperative with said element to receive said oscillations and a channel of rutile contiguous to said layer so that said oscillations pass from said layer to said channel.

5. In combination, a generator of high fre- -quency electrical oscillations having an output Where n is an even integer and A is the wavelength of said oscillations in said material cooperative with said element to receive said oscillations and a channel of rutile contiguous to said layer so that said oscillations pass from said layer to said channel.

6. In combination, a first resonator comprising a hollow conductor substantially filled with a material having a dielectric constant of the order of 100, means for transmitting a stream of electrical charges through said resonator in such manner that the velocity of said stream is modulated by the oscillation of said resonator, a second resonator comprising a hollow conductor substantially filled with a material having a dielectric constant of the order of 100 tuned to the same frequency as said first resonator and so spaced from said first resonator as to receive said stream of electrical charges and absorb energy in communication with said second resonator to derive energy therefrom.

7. In combination, a first resonator comprising a hollow conductor, substantially filled with rutile, means for transmitting a stream of electrical charges through said resonator in such manner that the velocity of said stream is modulated by the oscillation of said resonator, a second resonator comprising a hollow conductor substantially filled with rutile tuned to the same from said first resonator as to receive said stream of electrical charges and absorb energy therefrom, means for intercoupling said resonators electrically, and a channel of rutile in communication with said second resonator to derive energy therefrom.

. 8. In combination, a first resonator comprising a hollow conductor substantially filled with a material having a dielectric constant of the order of 100, means for transmitting a stream 01 electrical charges through said resonator in such manner that the velocity of said stream is modulated by the oscillation of said resonator, a second resonator comprising a hollow conductor substantially filled with a material having a dielectric constant of the order of 100 .tuned to the same frequency as said first resonator and so spaced from saidfirst resonator as to receive said stream of electrical charges and absorb energy therefrom, means for intercoupling said resonators electrically, a channel of a material having a dielectric constant 01! the order of 100 in communication with said second resonator to derive energy therefrom, and a layer of a material having a dielectric constant 01 the order of 10 contiguous to said channel to transmit said energy.

9. In combination, a first resonator comprising a hollow conductor substantially filled with a material having a dielectric constant of the order of 100, means for transmitting a stream of electrical charges through said resonator in such manner that the velocity of said stream is modulated by the oscillationo f said resonator, a second resonator comprising a hollow conductor substantially filled with a material having a dielectric constant of the order of 100 tuned to the same frequency as said first resonator. and

frequency as said first resonator and so spaced so spaced from said first resonator as to receive said stream of electrical charges and absorb energy therefrom, means for intercoupling said resonators electrically, a channel of a material length corresponding to said frequency in said material.

10. In combinationfa generator of high irequency electrical oscillations having an output element, a layer of dielectric material having a thickness substantially equal to where n is an even integer and A is the wavelength of said oscillations in said material, cooperative with said element to receive said oscillations and a channel of a dielectric material having a higher dielectric constant contiguous to said layer so that said oscillations pass from' a substantially higher dielectric constant than 5 the material of said layer, contiguous to said layer so that said oscillations pass from said layer to said channel, the dielectric constants of said layer and said channel and the thickness a of said layer being so selected that boundary refiection losses are suppressed.

- BENEDICT CASSEN. 

